Standard detectors of slow neutrons rely on the 10B(n,α), 6Li(n,α), or 3He(n,p) reactions. The thermal neutron cross-section for the 10B(n,α) reaction is 3840 barns, and the natural abundance of 10B is 19.8%. The most common detector based on the boron reaction is a BF3 gas tube. Boron-loaded scintillators are also used, although they encounter the challenge of discriminating between gamma rays backgrounds and gamma rays due to neutrons. The thermal neutron cross-section for the 6Li(n,α) reaction is 940 barns, and the natural abundance of 6Li is only 7.4%. This requires enrichment of 6Li isotope, and increases the cost of the scintillators in which 6Li is embedded. The thermal neutron cross-section for the 3He(n,p) reaction is 5330 barns, but its natural abundance of only 0.0001% results in even higher cost than 6Li. A further problem with all of these neutron detection methods is the need for active electronics to detect the particle emitted from the nucleus that has absorbed a neutron, increasing size, cost, and danger of compromising the mission if used for clandestine activities.
In addition to the problems discussed above, some applications may benefit from the availability of miniaturized monitors of thermal neutron exposure, which are presently not available. The present invention fills in this need and provides novel dysprosium-based nanocrystalline detectors.